Chapter 3: Program Statements
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Transcript Chapter 3: Program Statements
Infinite Loops
The body of a while loop eventually must make the
condition false
If not, it is an infinite loop, which will execute until the
user interrupts the program
This is a common logical error
You should always double check to ensure that your
loops will terminate normally
See Forever.java (page 165)
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Nested Loops
Similar to nested if statements, loops can be nested as
well
That is, the body of a loop can contain another loop
Each time through the outer loop, the inner loop goes
through its full set of iterations
See PalindromeTester.java (page 167)
The StringTokenizer Class
The elements that comprise a string are referred to as
tokens
The process of extracting these elements is called
tokenizing
Characters that separate one token from another are
called delimiters
The StringTokenizer class, which is defined in the
java.util package, is used to separate a string into
tokens
The StringTokenizer Class
The default delimiters are space, tab, carriage return, and
the new line characters
The nextToken method returns the next token
(substring) from the string
The hasMoreTokens returns a boolean indicating if
there are more tokens to process
See CountWords.java (page 172)
Choosing a Loop Structure
When you can’t determine how many times you want to
execute the loop body, use a while statement or a do
statement
• If it might be zero or more times, use a while statement
• If it will be at least once, use a do statement
If you can determine how many times you want to
execute the loop body, use a for statement